1. Field of the Invention
The present invention relates to a technique for generating highly concentrated ozone gas and particularly to a method and an apparatus for continuously generating highly concentrated ozone gas.
2. Description of Prior Art
There is conventionally proposed an apparatus for concentrating ozone gas which supplies to adsorption columns each filled with silica gel or the like adsorbent, ozone gas, generated by an ozonizer and controls a temperature of the adsorbent within each ozone gas adsorption column, thereby enabling the adsorbent to adsorb and desorb the ozone gas (International Publication WO96/24554).
This conventional apparatus for concentrating ozone gas comprises a plurality of adsorption columns arranged in parallel with each other and each filled with an adsorbent which gives priority to ozone gas adsorption. And it controls a temperature of the adsorbent within each adsorption column, thereby enabling the adsorbent to adsorb and desorb the ozone gas and supplies the concentrated ozone gas desorbed from each adsorption column under a constant pressure to an ozone using installation (user) through a concentration stabilizer.
3. Problems Presented by the Prior Art
Even in the case where ozone gas of about 5 to 7 vol % generated by an ozonizer is selectively saturation-adsorbed by cooled silica gel or the like adsorbent to concentrate it, the adsorbent adsorbs oxygen together with ozone gas. Therefore, the ozone gas can be concentrated only to the degree of about 70 vol %. Further, as for an apparatus which effects the ozone gas desorption by regulating a temperature of the adsorbent, it is well known the desorbed ozone gas changes its concentration and flow amount depending on the regulated temperature as time goes by and therefore does not stabilize itself. Besides, the conventional apparatus is arranged to take out the concentrated ozone gas from the adsorption column with scavenging gas when desorbing the ozone gas from the adsorption column. The thus taken out concentrated ozone gas reduces its concentration by an amount corresponding to the used amount of the scavenging gas. Accordingly, there was a problem it was difficult to send ozone gas of a constant concentration in a constant flow amount to an ozone gas using installation.
The present invention has an object to provide a method and an apparatus for generating highly concentrated ozone gas which can supply ozone gas of a constant concentration in a constant flow amount.
The present invention has another object to provide a method for concentrating ozone gas which enables an ozone gas adsorbent to adsorb ozone gas in a high concentration.
According to a first aspect of the present invention, there is provided a method for generating highly concentrated ozone gas which adsorbs ozone gas generated by an ozonizer with an adsorbent within each of adsorption columns and then supplies highly concentrated ozone gas separated from the adsorbent to an ozone gas using installation. In this method, an ozone gas concentrating unit comprises three adsorption columns arranged in parallel with each other and each filled with an adsorbent. Every adsorption column of this ozone gas concentrating unit is controlled so as to repeat four steps of: an ozone gas adsorbing step; a stabilizing and pressurizing step; an ozone gas desorbing step; and a cooling down step. Each of the ozone gas adsorbing step and the ozone gas desorbing step has operation time set twice the operation time of each of the stabilizing and pressurizing step and the cooling down step. The three adsorption columns composing the ozone concentrating unit are set to operate one after another by ⅓ (one third) cycle lag. The highly concentrated ozone gas separated at the desorbing step of each adsorption column is stored in an ozone gas storage vessel, from which the highly concentrated ozone gas is supplied to the ozone gas using installation after a flow controller has regulated its flow amount to a constant one.
According to a second aspect of the present invention, there is provided a method which includes adsorbing ozone gas with an ozone gas adsorbent and reducing an inner pressure of each ozone gas adsorption column. The second aspect of the invention further includes reducing the inner pressure to not more than a partial pressure of ozone gas.
According to another general aspect of the present invention, there is provided an apparatus for generating highly concentrated ozone gas which comprises ozone gas adsorption columns each filled with an ozone gas adsorbent and an ozonizer connected thereto, each ozone gas adsorption column being thermally controlled. In this apparatus, an ozone gas concentrating unit comprises three adsorption columns arranged in parallel with each other. Each of the adsorption columns has a gas introduction inlet connected to a common gas introduction valve. An ozonizer is arranged in the common gas introduction passage. Each of the adsorption column composing the ozone gas concentrating unit has a gas lead-out outlet continued to a gas lead-out passage, which is connected to a common gas discharge passage and a common gas take-out passage through respective flow passage switch-over valves. An ozone gas decomposer is interposed in the common gas discharge passage. The common gas take-out passage is connected to an ozone gas storage vessel. The respective adsorption columns in the ozone gas concentrating unit are adapted to change their operation modes one after another by ⅓ cycle.
The present invention combines into one set three ozone gas adsorption columns, each of which gives priority to ozone gas adsorption through being cooled and heated. Each of the ozone gas adsorption columns operates in a cycle which comprises an ozone gas adsorbing step, a stabilizing and pressurizing step, an ozone gas desorbing step and a cooling down step. Each of the ozone gas adsorbing step and the ozone gas desorbing step has operation time set twice the operation time of each of the stabilizing and pressurizing step and the cooling down step. The respective ozone gas adsorption columns operate one after another by ⅓ cycle lag. Accordingly, it is possible to make constant the concentration and flow amount of the ozone gas generated by the ozonizer. In addition, the ozone gas storage vessel is adjusted to once store the ozone gas led out of each adsorption column without employing carrier gas and therefore can absorb the change of concentration of the ozone gas separated from each adsorption column to result in a possibility of continuously supplying highly concentrated ozone gas to the ozone gas using installation.